The
International Space Station won't have to fire its thrusters Saturday to avoid
a close call with part of a spent rocket that launched a comet probe 10 years
ago, NASA officials said.
NASA's
Mission Control center in Houston spent Friday tracking the piece of a defunct
Delta 2 rocket that launched the agency's Stardust probe toward the comet
Wild 2 (pronounced "Vilt 2") in 1999, ultimately finding that it will
pass well clear of the station when it zooms by.
The debris
is now expected to pass within about 5 1/2 miles (9 km) of the station, nearly
twice as far away as initially thought, during its closest approach Saturday at
6:05 p.m. EST (2305 GMT). It is steadily moving away from the space station and poses no threat, NASA
officials said.
In its
former life, the
space debris formed part of the rocket that launched NASA's Stardust
mission toward a 2004 rendezvous with Comet Wild 2. The probe's sample
canister collected bits of the distant comet and returned them to Earth in 2006.
The
Stardust carrier ship, now called
Stardust-NExT - is currently headed to a different comet called Tempel 1.
NASA's Deep Impact probe intentionally crashed a probe into Tempel 1 in 2005 to
study its interior. Stardust-NExT is designed to revisit the comet in February
2011 to see how it has changed.
Another
piece of space trash, the remains of an old experiment that hitchhiked to orbit
on a larger vehicle, is also expected to swing by the space station on Monday.
But that debris will miss the space station by a comfortable 8.6 miles (14 km)
and also poses no threat to the orbiting laboratory.
NASA had hoped
the space station wouldn't have to dodge the space junk since it would have complicated
and already busy time at the
orbiting laboratory.
A Russian
Soyuz spacecraft is due to depart the space station next week to return three
members of the outpost's five-man crew back to Earth on Dec. 1. A week later,
a disposable engine module that ferried a new Russian room to the station this month
is also due to cast off from the station, with another Soyuz carrying three
more astronauts poised to launch toward the orbiting lab on Dec. 22.
Moving the
space station Saturday would have impacted the timing for the Soyuz flights to
and from the station, said NASA space operations chief Bill Gerstenmaier on
Friday. He spoke at NASA's Kennedy Space Center in Florida, where just hours
earlier the
shuttle Atlantis landed to end its own 11-day flight to deliver about
27,250 pounds (12,360 kg) of spare parts to the station.
"We have to
be careful how we go about maneuvering the space station," Gerstenmaier said. "We
have to balance the landing, the other Soyuz launch and then make sure we've
tweaked it enough that we miss the object."
NASA typically
moves the station when the odds of a space debris impact are within a
1-in-10,000 chance. Mission Control also works to keep a safety perimeter that extends
15 miles (25 km) around the space station, as well as about a half-mile (0.75
km) above and below it.
The station
flies in an orbit about 220 miles (354 km) above Earth at a speed of about
17,500 mph (28,163 kph).
Space
debris has been a recurring concern for the space station and other spacecraft,
especially since the crash of two communications satellites earlier this year
and China's intentional destruction of a satellite in 2007 during an anti-satellite
test.
The growing
threat of space junk to orbital vehicles has sparked a renewed push to better
monitor, and possibly reduce, the more than 20,000 pieces of space junk
currently watched by tracking agencies.
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